APPLICATION OF A CRITICAL STATE BOUNDING SURFACE MODEL IMPLEMENTED IN MULTILAMINATE FRAMEWORK FOR NUMERICAL MODELING OF SOILS

ABSTRACT: A new plasticity model is proposed based on implementing a critical state based bounding surface model in multilaminate framework. The original bounding surface model is defined by the following four surfaces: (i) failure surface (ii) bounding surface; (iii) loading surface and (iv) plastic dilatancy surface. These surfaces are defined in multilaminate framework to introduce a new constitutive model. In this framework, the failure, bounding, loading and plasticity dilatancy surfaces are formulated on 2 x 13 local planes with varying orientations over a virtual unit sphere around a stress point. A weight factor is assigned to each plane with respect to the volume of the unit sphere. The overall response of the material when subjected to a load will then be integrated by summation of the contributions of all planes. The model parameters are calibrated by modeling nine triaxial tests under different densities and confining stresses. Application of the new constitutive model is then studied by its implementation into a finite difference code and modeling a soil-pipe laboratory test. It is concluded that the new constitutive model could accurately predict the observed triaxial and laboratory tests.